A lifter device used for a seat of a vehicle or the like is adapted to adjust the height of a seat cushion to a floor by operating an operation handle, and various types of lifter devices have been developed. In the invention disclosed in JP-A-2016-132423, when an operation handle is operated to a seat lifting side or a seat lowering side, the height adjustment is performed by a fixed amount for each operation, and the operation of the operation handle is repeated until a seated person reaches a desired height.
Specifically, a rotation control device is configured to rotate a pinion gear coupled to a link mechanism so as to lift or lower a seat by operating the operation handle to the seat lifting side or the seat lowering side. In the rotation control device, a rotation driving mechanism for rotationally driving the pinion gear and the lock mechanism for locking the rotation of the pinion gear are provided to a rotation shaft of the pinion gear.
The lock mechanism includes a ratchet wheel which rotates in synchronization with the rotation shaft and has an engaging claw formed on its outer periphery, a pawl which is held on a support member so as to be prevented from moving in a rotational direction of the rotation shaft and to be movable inward in a radial direction of the rotation shaft and which is provided to be engageable with the engaging claw of the ratchet wheel from an outer peripheral side, a spring which biases the pawl in a direction of engaging with the ratchet wheel, and a pawl operating member which brings the pawl into an engagement state with ratchet wheel in a non-operated state of the operation handle, which brings the pawl into a free state when the operation handle is operated to the seat lifting side, and which separates the pawl from the ratchet wheel when the operation handle is operated to the seat lowering side. Further, the engaging claw of the ratchet wheel has a shape that does not engage with the pawl when the ratchet wheel is rotated in the lifting direction together with the rotation shaft and that engages with the pawl when the ratchet wheel is rotated in the lowering direction together with the rotation shaft.
When the operation handle is operated to the seat lifting side, the pinion gear is rotationally driven to lift the seat by the rotation driving mechanism. At this time, the lock mechanism locks the rotation of the pinion gear by engaging the pawl with the ratchet wheel at the position where the pinion gear is rotated by the operation of the operation handle.
When the operation handle is operated to the seat lowering side, the rotation driving mechanism does not function, and the lock mechanism separates the pawl from the ratchet wheel to release the locking of the pinion gear. In this way, the pinion gear is rotated in the direction of lowering the seat. At this time, in order to suppress the lowering speed of the seat, the speed is suppressed by a damper coupled to the rotation shaft of the pinion gear.
In a state where the operation handle is not operated, the pawl is engaged with the ratchet wheel and the rotation of the pinion gear is locked by the lock mechanism, so that the height of the seat is maintained.
In order for the lock mechanism to be actuated in accordance with the operation of the operation handle, it is necessary to control the relationship between the pawl and the ratchet wheel in a designed state according to the operation of the operation handle. Therefore, the pawl operating member is brought into a reference position in the non-operated state of the operation handle, and the pawl operating member is moved around the reference position in accordance with the operation of the operation handle.
The alignment of the pawl operating member to the reference position is performed by making the rotational position of the pawl operating member coincide with the support member supporting the rotation shaft. However, in the invention disclosed in JP-A-2016-132423, there is a problem that the number of parts to be interposed between the support member and the pawl operating member is increased when the rotational position of the pawl operating member is aligned to the reference position with respect to the support member. Therefore, in order to align the pawl operating member with the support member with high accuracy, it is necessary to enhance the dimensional accuracy of the parts to be interposed, which causes an increase in cost.